The present invention relates to human body detection devices, and more particularly to a device which is composed of a pyroelectric-type sensor for detecting the presence of a human body and an infrared distance-measuring sensor for computing a distance to a human body in combination.
The present invention further relates to electronic equipment which is provided with the human body detection device described above.
The expression “electronic equipment” as used herein broadly denotes devices which execute electric processing using an output outputted from a human body detection device.
In recent years, a device composed of a pyroelectric-type sensor for detecting the presence of a human body and an infrared distance-measuring sensor (referred to as “human body detection device”) has been suggested in order to detect a human body without the need for physical contact between a human body and the device. A pyroelectric-type sensor detects not a stationary body itself but the heat rays (far infrared rays) emitted from the body and thus has a merit that it can sense the presence of a human body. While the pyroelectric-type sensor has a wide angle of field (approx. ±50 degree horizontally) and a long detection distance (up to 5 meter), it cannot detect a distance to and a direction of a human body. On the other hand, an infrared distance-measuring sensor, which emits near infrared rays from an infrared-ray emitting device, detects reflected light beams from a detection object using a position sensing device (PSD). While the infrared distance-measuring sensor has a narrow angle of field (a few degree), it can detect a distance to a detection object, being hardly affected by the colors of the object (the clothing a human body wears). Therefore, combination of the pyroelectric-type sensor and the infrared distance-measuring sensor allows detection of not only the presence of a human body but also a distance to and a direction of a human body (see, e.g., JP H08-338880A).
FIG. 1A is an overhead view schematically showing a conventional human body detection device 100 and FIG. 1B is a front view schematically showing the interior construction of the conventional human body detection device 100. As shown in FIG. 1B, the human body detection device 100 is provided with a pyroelectric-type sensor 101 for detecting the presence of a human body and a plurality of infrared distance-measuring sensors 102-0, 102-1, 102-2, 102-3 and 102-4 (hereinafter collectively referred to as 102) for detecting a distance to a detection object (a human body) in a body casing 150. Each of the infrared distance-measuring sensors 102, being independently and equivalently constituted, is provided with an infrared-ray emitting device (LED) 103, a position sensing device (PSD) 104 and an integrated circuit (IC) 109 in a housing 108. The infrared distance-measuring sensors 102 are arranged in various directions for measuring a distance so that the plural sensors cover the whole detection range of the pyroelectric-type sensor 101. As shown in FIG. 1A, converging lenses 105 and 106 are arranged on a front surface of the casing 150, each of the lenses corresponding to the LEDs 103 and the PSD 104. Near infrared rays emitted from each of the LEDs 103 reach a detection object H through the corresponding converging lens 105, and enter a light receiving surface of the PSD 104 through the converging lens 106. The PSD 104 outputs a signal showing a distance up to the detection object H based on a position on the light receiving surface where the reflected light beams enter.
As shown in FIG. 2, the pyroelectric-type sensor 101 contains a sensor part 101a and a signal processing circuit 101b for processing an output signal from the sensor part 101a. Although only one distance-measuring sensor 102-0 is shown in detail in FIG. 2, each of the distance-measuring sensors 102 contains an LED driving circuit 103B for driving each of the LEDs 103, a signal processing circuit 104B for processing an output from the PSD 104, and a resistor 104C for adjusting sensitivity (103B, 104B and 104C correspond to IC 109 in FIG. 1). The body casing 150 is also provided with a constant-voltage circuit 130 for supplying a constant voltage with each of the distance-measuring sensors 102 and a control circuit 140 for controlling each of the distance-measuring sensors 102.
The pyroelectric-type sensor 101 is always set to an operational state. When a detection object (shown as a human body H in FIG. 1A) exists within a prescribed range (a detection range) from the pyroelectric-type sensor 101, the pyroelectric-type sensor 101 detects far infrared rays emitted from the human body, and outputs a detection signal. According to the detection signal, a distance measuring operation of the distance-measuring sensor 102 is started by a control of the control part 140. Ordinarily, distance measuring operations are intermittently repeated by 102-0, 102-1, 102-2, 102-3 and 102-4 in order. When the distance-measuring sensors 102 detect a distance to a detection object during the operation, a position of a human body relative to the human body detection device 100 is specified based on a direction and a distance of the human body.
However, in the case of the human body detection device 100 in which a plurality of distance-measuring sensors 102 independently composed in respective housing 108 is used, the whole device is necessarily of a large size, resulting in a restriction in use such that the device cannot be mounted on a small-sized equipment. Additionally, the device becomes expensive due to the larger number of its parts.